Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
642 PM EDT Thu Aug 13 2020
Valid 12Z Mon Aug 17 2020 - 12Z Fri Aug 21 2020
...Guidance Evaluation and Preferences...
Overall, model/ensemble guidance showed near to above average
consensus through the extended forecast period. A blend of the 12Z
ECMWF/CMC was used heavily as a forecast starting point initially
on day 4 (Mon). A gradual trend toward increased weight placed on
ensemble means (ECENS/NAEFS) was shown through time, with majority
ensembles in the blend during days 7-8 (Thu-Fri). Overall,
guidance is consistent in showing a fairly amplified pattern
continuing, with an upper trough persistent across the Gulf of
Alaska, and ridging attempting to build across the Bering Sea next
week.
...Weather Highlights/Threats...
A low pressure system across the Gulf of Alaska will weaken by
early next week, but could bring heavy rain to portions of the
Alaska Panhandle into Monday. A second low pressure system is
forecast to cross the Bering Sea Mon, with a triple point low near
the Alaska Peninsula becoming dominant by Tue, and the system
expected to once again move east across the Gulf of Alaska from
there through the middle/end of next week, keeping precipitation a
distinct possibility across southern mainland Alaska as well as
the Panhandle. Farther north, a weakening frontal boundary
expected to settle into the Interior should bring scattered
showers by next Tue-Wed. By later next week, as upper ridging
potentially builds across the Bering Sea and western mainland
Alaska, drier conditions should prevail across much of mainland,
with only the Panhandle/Southeast Alaska remaining wet. In
general, this pattern should favor temperatures several degrees
above average across much of the state. The North Slope will see
decreasing temperatures in the wake of the cold front next week,
with high temperatures expected to drop to a few degrees below
average.
Ryan
Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php
Hazards:
- Heavy rain across portions of the Alaska Panhandle, Sun-Mon, Aug
16-Aug 17.
WPC medium range Alaskan products including 500mb, surface
fronts/pressures progs and sensible weather grids can also be
found at:
https://www.wpc.ncep.noaa.gov/alaska/ak_5dayfcst500_wbg.gif
https://www.wpc.ncep.noaa.gov/alaska/akmedr.shtml
https://www.wpc.ncep.noaa.gov/alaska/ak_5km_gridsbody.html